The operating system is a special type of program that loads automatically when you start
your computer. The operating system allows you to use the advanced features of a modern
computer without having to learn all the details of how the hardware works. There are a
number of different types of operating system in common use.
The IBM PC (Personal Computer) was introduced way back in 1981 and was originally supplied with an
operating system called DOS (Disk Operating System). This operating system was very
basic, and you had to be a bit of a computer expert just to understand how to use it. It was
NOT user-friendly. Later on, Microsoft introduced Windows and this is the operating
system that is most widely used on PCs today. To complicate matters further, there are a
number of different types of Windows. The first widely used version of Windows was
called Windows 3.1. This was more powerful than DOS and far easier to use. It had a
Graphical User Interface (GUI), i.e. you could 'drive' it using a mouse and drop down
menus. Later versions of Windows include Windows 95, Windows NT, Windows 98,
Windows 2000 and Windows XP. The good news is that later versions of Microsoft
Windows look almost identical to each other and are all much easier to use than Windows
3.1.

IBM produced an operating system called OS/2 but this was largely ignored and is only
used by a few companies.
UNIX and Linux are other examples of operating systems that may be run on PCs
Other types of computers, such as those manufactured by Apple have a completely
different operating system.

What is a Graphical User Interface?
GUI

· A Graphical User Interface (GUI) is simply an additional part of the operating system that
displays windows and drop down menus, and also enables you to drive your computer
using a mouse. Examples of operating system that use a GUI include Windows and IBM's
OS/2.
The advantages of using a GUI

· All programs look similar and when you switch from a program supplied by one
manufacturer to one from a different manufacturer, you will find the transition very easy.
1· Application programs work in the same way as the underlying operating system.
2
· The GUI also allows programmers to easily write consistent looking programs.
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